168 VEGETARIANS AND THEIR TEETH 



the canines is the presence of a gap (or "diastema" as it is called) 

 between the four front teeth or incisors of the upper jaw and the upper 

 canine which allows the lower canine to fit in front of the upper canine 

 when the jaw is closed. The number of the tubercles or cones on the 

 molars (the two smaller pre-molars and the three hinder large molars) 

 can be compared in detail in these beautiful drawings from Professor 

 Selenka's work, which are the most careful and perfect which have 

 ever been published. The agreement of these teeth in man and the 

 gibbon is very close : but there are differences. The first, or most 

 anterior premolar of the lower jaw has one predominant cusp or cone ; 

 the second, like both in the upper jaw, is "bicuspid," or bi-tuberculate, 

 as in man. The three big molars of the upper jaw are closely similar to 

 those of man, with some small differences, the second being quadri- 

 tuberculate, whilst in man it is as often tri-tuberculate (as it is in PI. VII) 

 as it is quadri-tuberculate. But the two anterior big molars of the 

 lower jaw are seen to have each five well-marked cones, cusps or 

 tubercles; they are quinqui-tuberculate, whilst in man the first lower 

 molar is often quadri-tuberculate and the second even more frequently so. 

 The last lower molar (wisdom tooth) of the gibbon is like that of 

 man, quadri-tuberculate. 



The details of the tubercles on these molar teeth distinctly justify 

 the conclusion that they are adapted in the two animals compared- 

 namely, man and the gibbon to food of the same mechanical quality, 

 and this undoubtedly is fruit and nuts. Nevertheless such a form of 

 tooth is equally well adapted to the texture of cooked meat, which has 

 served many races of man for probably hundreds of thousands of years 

 as food. 



